Influence of ceramic waste powder on shear performance of environmentally friendly reinforced concrete beams

This investigation considered the usability of ceramic waste powder (CWP) in altered quantities in reinforced concrete beams (RCBs). In this way, it was aimed to reduce the environmental impacts of concrete by using CWP as a raw material in RCBs. 12 small-scale shear RCBs with the dimensions of 100 × 150 × 1000 mm were tested in this study. The variations of stirrups spacing and CWP ratio were examined in these specimens. The percentages of CWP by weight utilized in RCBs were 10%, 20%, and 30%, and stirrups spacings were adopted as 270 mm, 200 mm, and 160 mm. At the end of the study, it was determined that more than 10% CWP additive negatively affected the RCBs' compressive strength. The load-carrying capacity reduced between 30.3% and 59.4% when CWP increased from 0% to 30% as compared to RCB with stirrups spacing of 270 mm without CWP. However, compared to RCB with stirrups spacings of 200 mm and 160 mm without CWP, there were decreases in the load-carrying capacity as 21.4%–54.3% and 18.6%–54.6%, respectively. While the CWP ratio increased, the specimens with 160 mm, 200 mm, and 270 mm stirrups spacings obtained a lower maximum load value. However, with the increase of the CWP ratio in the specimens with 160 mm stirrups spacing, RCBs reached the maximum load-carrying capacity at an earlier displacement value. When stirrups spacing was selected as 270 mm, it was observed that the maximum load-carrying capacity of RCBs reached at a similar displacement value as the CWP ratio increased. Besides, it was resulted that the bending stiffness of RCBs reduced as the quantity of CWP enhanced. The bending stiffness decreased by 29.1% to 66.4% in the specimens with 270 mm stirrups spacing, 36.3% to 20.2% with 200 mm stirrups spacing, and 10.3% to 36.9% with 160 mm stirrups spacing. As an implication of the experiments, the use of CWP up to 10% in RCBs was realized as an economical and environmental approach and is suggested. There is some evidence to report that making use of CWP may be considered to be ecologically benign. This is due to the fact that reusing CWP may significantly reduce CO2 emissions, save energy, and reduce total power consumption. Furthermore, the experimental results were compared to the analytical calculations.


Materials and methods
In this study, to make eco-friendly RCBs, CWP replaced some portions of cement.A fixed mixture design (Table 1) with changing the cement ratio was used.CWP was employed as 10%, 20%, and 30% of the cement weight.The utilized CWP is presented in Fig. 1.The mechanical strengths of the samples are illustrated in Fig. 2. A slight decrease in the mechanical strengths was observed when 10% of CWP was utilized to replace cement.However, this reduction significantly grew after 10% of CWP.
A shear collapse without any prior warning is likely to happen abruptly in a beam that lacks appropriately designed shear reinforcements when it is overloaded to the point of failure (brittle failure).Therefore, to ensure that flexural damage would occur before the shear failure, concrete must be given with special shear reinforcements.Through the current experimental program, the impacts of stirrups spacing on the shear behavior and shear capacity of RCBs with minimal shear reinforcements were examined.In other words, the influence of stirrups on the shear-carrying capacity in the tested RCBs was significant and might hinder the observation of the effect of CWP.Consequently, the contribution of CWP was tried to be understood by considering different stirrups spacings.Additionally, as the CWP percentages changed, RCBs were tested to assess the effectiveness of the changes in their performance.In this way, the ductility, stiffness, and energy dissipation of the specimens were evaluated with respect to the stirrups spacings and CWP percentages.To achieve this objective, the load-carrying capacities of RCBs were assessed.The spacings between stirrups were set at 160 mm, 200 mm, and 270 mm, while the specimens were tested with varying percentages (0%, 10%, 20%, and 30%) of the CWP additions.The results were then compared to those of the reference specimens.The experimental test specimens are depicted   www.nature.com/scientificreports/ in Fig. 3.A total of 12 RCBs were produced to examine the shear capacity of the CWP-contributed beams.This study investigated the RCBs' shear performance using CWP concrete mixture in certain proportions instead of cement.The size of the specimens was planned as 100 × 150 × 1000 mm.In addition, as can be seen in Fig. 4, each specimen was evaluated under four-point bending tests.Altered main parameters were considered to assess the implications of CWPs on the shear performance, weight ratios of CWP, and spacings of stirrups.The weight percentages of 0%, 10%, 20%, and 30% CWP were used, while stirrups spacings of 270 mm, 200 mm, and 160 mm were considered.The longitudinal reinforcements utilized for the tension and compression sections were selected as 2Ø12 and 2Ø6, respectively, as indicated in Fig. 3.The specifications of the test samples are listed in Table 2.

Efficiency of altered stirrups spacings
In this section, RCBs were tested with altered stirrups spacings to examine the efficiency of the stirrups.Details are presented in the following.of CWP-contributed specimens suffered from the shear damage at the end of the tests.The curves provide a detailed representation of the crack formations in RCBs (Fig. 8).

Case 3: Rupture and load-displacement form of RCBs (S-CERAMIC#4, S-CERAMIC#5, and S-CERAMIC#6)
The failure patterns and load-displacement relations of the samples with 20% CWP ratio instead of the cement amount by weight are displayed in Figs. 9 and 10.In Fig. 9, the specimens had the shear damage at the end of the experiment, similar to Case 1 and Case 2, and collapsed.The rise in the CWP ratio resulted in a decline in the load-carrying capacity.Based on Fig.    29 kN and a P max displacement of 9.57 mm.Consequently, the rise in the CWP rate to 30% resulted in a decline in the load-carrying capacity.Moreover, it is shown that the load-displacement capacities of RCBs expanded gradually as stirrups spacing decreased.This suggests that stirrups spacing had an efficient effect on the load-displacement capacities of RCBs.It was noticed that these results were similar to those in Case 1, Case 2, and Case 3.However, the increase in the CWP ratio caused the maximum load values of RCBs to approach each other.When Figs. 6, 8, 10, and 12 are evaluated, it is clear that the reference specimens had a maximum load-carrying capacity for all stirrups spacings.As the CWP ratio decreased, the load values were obtained closer to the reference specimens.In other words, in the RCB specimens with spacings of stirrups as 160 mm, 200 mm, and 270 mm, the CWP additives as 0%, 10%, 20%, and 30% reduced the load-carrying capacities of RCBs compared to the reference specimens, respectively, as 18.6%, 36.1%, and 54.6% (for 160 mm stirrups spacing), 21.4%, 41.8%, and 54.3% (for 200 mm stirrups spacing), and 30.3%, 47.8, and 59.4% (for 270 mm stirrups spacing).Furthermore, although this reduction in the load-carrying capacity of RCBs was related to the quantity of CWP, it was not linear.In addition, the load-carrying capacity decreased as stirrups spacing increased.As stirrups spacing in the samples decreased (270 mm > 200 mm > 160 mm), the load-carrying capacity was negatively affected by rising rates of CWP (10% < 20% < 30%).www.nature.com/scientificreports/

Efficiency of altered percentages of CWP
RCBs were also tested with altered CWP percentages to assess their efficiency on the performance of RCBs.For this purpose, the weight percentages of 0%, 10%, 20%, and 30% CWP were adopted and tested.

Case 1: Rupture and load-displacement form of RCBs with different percentages of CWP and spacing of stirrups as 160 mm
The evaluation of RCBs with constant stirrups spacing and different CWP ratios is explained in this section.The amounts of CWP were taken as 0%, 10%, 20%, and 30% while stirrups were constantly spaced 160 mm apart.The failure modes of RCBs are depicted in Fig. 13.Based on Fig. 14, the maximum load was acquired as 61.03 kN, and the P max displacement was achieved as 13.10 mm when the CWP ratio was set to 0% (S-REF#3).For a CWP ratio of 10% (S-CERAMIC#3), the maximum load and P max displacement were 49.65 kN and 11.88 mm, respectively.The maximum load and P max displacement were found to be 38.94kN and 9.58 mm, respectively, when the CWP ratio increased to 20% (S-CERAMIC#6).After increasing the CWP ratio to 30% (S-CERAMIC#9), it was resulted that the maximum load and P max displacement were reduced to 27.68 kN and 9.42 mm, respectively.However, the load-carrying capacity of S-CERAMIC#3, S-CERAMIC#6, and S-CERAMIC#9 specimens dropped by 18.6%, 36.1%, and 54.6%, respectively, in comparison to S-REF#3.This pointed out that increasing the CWP additive decreased the load-carrying capacity.In addition, depending on the increased CWP ratio, RCBs reached the maximum load value at an earlier displacement value.The findings revealed that the structural features of RCBs declined as the replacement rate of CWP reached 10% or higher.This was ascribed to a diluting effect and increased CWP porosity that negatively impacted the microstructure and properties of concrete (Rachied et al.  www.nature.com/scientificreports/2023).The decrease in the strength is consistent with the dilution effect and increased porosity, which disrupt the concrete microstructure and hinder the strength growth.

Case 2: Rupture and load-displacement form of RCBs with different percentages of CWP and spacing of stirrups as 200 mm
Here, spacing of stirrups in RCBs was constantly conisdered as 200 mm, while the amounts of CWP were 0%, 10%, 20%, and 30% to examine the efficiency of the altered CWP percentages.The failure patterns of the tested RCBs with 0%, 10%, 20%, and 30% CWP are indicated in Fig. 15.As can be observed from Fig. 16, the P max displacement measured was 13.01 mm, maximum load was 55.88 kN, and CWP ratio was 0% (S-REF#2).Where the 10% (S-CERAMIC#2) CWP ratio was chosen, the maximum load and P max displacement were 16.03 mm and 43.87 kN, respectively.It was discovered that the maximum load and P max displacement decreased to 32.47 kN and 9.49 mm, respectively when the CWP ratio rose to 20% (S-CERAMIC#5).This was followed by a decrease in the maximum load and P max displacement to 25.51 kN and 8.84 mm, respectively, when the CWP ratio increased to 30% (S-CERAMIC#8).On the other hand, the load-carrying capacity of S-CERAMIC#2, S-CERAMIC#5, and S-CERAMIC#8 samples decreased by 21.4%, 41.8%, and 54.3%, respectively, when compared to S-REF#2.These findings demonstrated that the use of the CWP additive led to a greater reduction in the load-carrying capacity as the stirrups spacing increased.In addition, it was determined in Figs. 15 and 16 that the stiffness of the samples decreased and cracks increased with the increase of the CWP ratio.

Case 3: Rupture and load-displacement form of RCBs with different percentages of CWP and spacing of stirrups as 270 mm
In order to evaluate the efficiency of an altered CWP percentage, the amounts of CWP were taken as 0%, 10%, 20%, and 30% when spacing of stirrups in RCBs was constant as 270 mm.The results of the experimental  tests on RCBs with 0%, 10%, 20%, and 30% CWP are presented in Fig. 17.Based on Fig. 18, for the CWP ratio as 0% (S-REF#1), the maximum load was obtained as 45.11 kN and P max displacement was found as 7.92 mm.The 10% (S-CERAMIC#1) CWP ratio resulted in the maximum load and P max displacement of 31.43 kN and 7.78 mm, respectively.It was seen that the highest load and highest P max displacement decreased to 23.51 kN and 8.69 mm when the CWP ratio rose to 20% (S-CERAMIC#4).Subsequently, when the CWP ratio increased to 30% (S-CERAMIC#7), it was observed that the highest load and P max displacement decreased to 18.29 kN and 9.57 mm, respectively.To clarify, when comparing S-REF#1 to S-CERAMIC#1, S-CERAMIC#4, and S-CERAMIC#7 samples, the load-carrying capacity declined by 30.3%, 47.8%, and 59.4%, respectively.This point displays that when stirrups spacing increased more, the CWP additive dramatically lowered the load-carrying capacity.It was also shown that the samples reached their maximum load-carrying capacity at approximately similar displacement values with increasing stirrups spacing.When the CWP ratio increased, at the same time, a significant decrease was witnessed in the initial stiffness values.This illustrated that CWP was less effective on stiffness as the stirrups spacing increased.
As can be noticed from Figs. 14, 16, and 18, the load-carrying capacity of RCBs diminished as the CWP quantity increased from 0% to 30%.The maximum load value reached by the samples decreased as the CWP ratio increased in the samples with stirrups spacings of 160 mm, 200 mm, and 270 mm.However, with the increase of the CWP ratio in the samples with 160 mm stirrups spacing, the samples reached the maximum load-carrying capacity at an earlier displacement value.While the space between the stirrups was chosen as 270 mm, it was observed that the maximum load-carrying capacity of the samples reached at a similar displacement value as the CWP ratio increased.In addition, it was detected that CWP reduced the quantity and range of the flexural ruptures in RCBs.www.nature.com/scientificreports/

Efficiency of altered percentages of CWP on ductility, stiffness, and energy dissipation
The stiffness, ductility, and energy dissipation values of the specimens are assessed by considering Tables 3 and  4. Sufficient ductility could not be achieved in all test samples.In the literature, the ductility ratio of RCBs with under-reinforced design was given between 4 and 5.The ductility ratios obtained in Table 3 are below this limit.
In addition, when the end-of-test damages of the samples are examined, it is understood that RCBs were generally subjected to the diagonal tension failure.The stiffness of the samples corresponding to the maximum load value decreased with increasing the CWP ratio.
The shear damages of the samples signify that they did not have sufficient energy dissipation capacity.However, the energy dissipation capacities for different levels were calculated and are presented in Table 4.The assessment can be made for the energy dissipation capacity corresponding to the maximum load level.As can be seen in Table 4, the energy dissipation capacity corresponding to the maximum load value decreased depending on the increase in stirrups spacing and CWP ratio.In the samples with the CWP ratios of 10%, 20%, and 30% and stirrups spacing of 270 mm, the respective reductions were determined as 28.3% (S-CERAMIC#1), 40.4% (S-CERAMIC#4), 49.1% (S-CERAMIC#7).The ratios exhibited an upward trend as the stirrups spacing  reduced.However, this increase was not due to the increase in the CWP ratio but because of the decrease in spacing of stirrups.Similar to the conclusions of the literature, it was identified that the factors affecting the energy dissipation were the cause of such ductility values 71 .To bear the increased loads operating on the construction, a structural element with a high degree of ductility is exposed to massive inelastic deformations.As an implication, the structural members undergo significant deformations before reaching the point of collapse 72 .The decrease in the resulting energy dissipation indicates that the structural element cannot withstand earthquakes largely because of a gradual failure mechanism.A comparison of the energy dissipation for altered quantity of CWP is depicted in Fig. 19.

Calculation of shear capacity
Different empirical approaches for calculating the shear capacity of RCBs are available in the literature.In an empirical calculation close to the experimental results, parameters such as the cylinder concrete strength (f′ c ), RCBs' width (b w ), shear span (a), stirrups spacing (s), reinforcement ratio (ρ), RCBs' effective depth (d), stirrups  ratio (A v /s), and yield stress (f yd ) of reinforcements should be known.The commonly used empirical formula in the shear capacity calculation, which is known to be close to the experimental results, is given in Eq. (1) 73 .
It can be detected in Fig. 20 that as the CWP percentage in RCBs increased, the change in the shear capacity rose.As a result of the comparison, the analytical results were obtained with an approximation of up to 3.2% of the experimental results.The comparison of the experimental and analytical results is presented in Table 5.When Table 5 is examined, the analytical and experimental results diverged, as the CWP ratio in RCBs increased.This situation points out that the equation needs to be developed for the analytical calculations of CWP-added concretes. (1)

Environmental values of CWP
More environmentally friendly and sustainable goods may be produced by recycling and using garbage that is solid in the production of building materials.These materials, however, must either be economically viable alternatives to currently used materials or have environmental advantages that justify their use.To assess the sustainability of CWP-mortar compared to regular mortar, it is necessary to choose metrics such as greenhouse gas emissions, production costs, and energy consumption related to mortar manufacture.The utilization of   CWP-mortar is primarily influenced by these criteria, which are regarded as the main factors, despite the presence of other significant indications that also contribute.Samadi et al. 74 evaluated the impact of substituting conventional Portland cement with a ceramic material on the emissions of greenhouse gases in a blended cement.
The study found that higher levels of ground ceramic in the mortar samples led to a decrease in the emissions of greenhouse gasses.Along with a rise in ground ceramic from 20% to 40%-60%, the density of the gases emitted was also decreased from 92.9 kg/m 3 to 77.5 kg/m 3 and 46.8 kg/m 3 .During the production of one ton of blended cement, which consisted of 40% ground ceramic, the emission of 1 m 3 of greenhouse gases occured, which represents a decrease of almost 37% compared to a conventional mixture 53 .Using CWP instead of typical aggregate will appear to have a huge environmental benefit, as can be demonstrated from the analyses above, even though the load-displacement curves are near to one other.Moreover, given the primary objective of employing CWP is to account for the environment, these statistics provide a significant perspective on quantifying the environmental advantages of adopting CWP.

Conclusions
This study investigated the change in the shear capacity of RCBs produced with the CWP additives at different rates experimentally and analytically.Stirrups spacings in the specimens were chosen as 270 mm, 200 mm, and 160 mm.The findings obtained as results of the study can be summarized as follows: • More than 10% CWP additive was determined to affect the concrete compressive strength negatively.
• The reference RCBs got the maximum load-carrying capaicty in all stirrups spacings (270 mm, 200 mm, and 160 mm).In the RCBs specimens, with stirrups spacings of 270 mm, 200 mm, and 160 mm, the CWP  • RCBs with different stirrups spacings, created with a 10% contribution of CWP, reduced the load-carrying capacity by 18.6% to 30.3%.This decrease reached 47.8% with a contribution of 20% CWP, and up to 54.3% with a contribution of 30% CWP.It was resulted that if the 10% CWP contribution was exceeded within the considered CWP ratios, the load-carrying capacity decreased too much.For different stirrups spacings, using 10% by weight of CWP may be recommended instead of cement.• The maximum load value reached by the samples decreased as the CWP ratio increased in the samples with stirrups spacings of 160 mm, 200 mm, and 270 mm.However, with an increased CWP ratio in the samples with 160 mm stirrups spacing, RCBs reached the maximum load-carrying capacity at an earlier displacement value.• When spacing between each stirrup was selected as 270 mm, it was observed that the maximum load-carrying capacity of RCBs reached at a similar displacement value as the CWP ratio increased.• It was determined that the bending stiffness of RCBs reduced, as the quantity of CWP enhanced.In other words, the bending stiffness decrease was between 29.1% and 66.4% in the specimens with 270 mm stirrups spacing, between 36.3% and 20.2% in the specimens with 200 mm stirrups spacing, and between 10.3% and 36.9% in the specimens with 160 mm stirrups spacing.• Evidence has shown that utilizing CWP can be regarded as an environmentally-friendly solution.This is because reusing CWP can substantially decrease CO 2 emissions, conserve energy, lower overall electricity consumption, and reduce fuel usage.Consequently, this leads to the global availability of a sustainable and cost-effective construction material.
Consequently, in this study, the use of CWP, a mutual and inexpensive waste, in concrete was investigated with a series of experimental tests on RCBs.By the empirical research, the use of CWP up to 10% in RCBs is recognized as a cheap and ecologist approach and is suggested.

Future work area
Additional testing and experimentation should be conducted on CWP to obtain its strength properties for use in typical or low-rise structural concrete applications.To get further insight into the workability, experimentation with different water/cement ratios may be done to determine the factors that affect the strength when sodium silicate is added.Moreover, the strength properties of CWP, which is also a pozzolanic material, may be further studied and researched.Studying CWP should be continued since it may help maintain the ecology and environment.

Figure 2 .
Figure 2. Mechanical strengths of samples with and without CWP.

Case 1 :
Rupture and load-displacement form of RCBs (S-REF#1, S-REF#2, and S-REF#3) As proffered in Figs. 5 and 6, the failure patterns and load-displacement diagrams of the RCB tests are observed, respectively.In Fig. 4, the maximum load-carrying capacity of S-REF#3 with 160 mm stirrups spacing was obtained as 61.03 kN, while the displacement at P max was 13.10 mm.The maximum load-carrying capacity value and displacement at P max of S-REF#2 and S-REF#1 specimens, in which the stirrups spacings were increased to 200 mm and 270 mm, were 55.88 kN and 13.01 mm and 45.11 kN and 7.92 mm, respectively.As a result, the specimens suffered from the shear damage earlier in the load-carrying capacity due to the increased stirrups spacings.Compared to S-REF#3, this ratio was 8.4% lower in S-REF#2 and 26% lower in S-REF#1.According to Fig. 5, all three specimens experienced the shear damage and collapsed.
www.nature.com/scientificreports/Case 4: Rupture and load-displacement form of RCBs (S-CERAMIC#7, S-CERAMIC#8, and S-CERAMIC#9) This section investigates the variation of the shear capacity by adding 30% CWP to RCBs with different stirrups spacings.The end-of-experiment damage and load-displacement relationship of each specimen are presented in Figs.11 and 12, respectively.In Fig.12, S-CERAMIC#9 specimen suffered from the sudden shear damage after reaching 27.68 kN.The P max displacement was obtained as 9.42 mm.Two specimens, S-CERAMIC#8 and S-CERAMIC#7, were tested with stirrups spacings of 200 mm and 270 mm, respectively.S-CERAMIC#8 specimen had a load capacity of 25.51 kN and a P max displacement of 8.84 mm, while S-CERAMIC#7 specimen had a load capacity of 18.

Figure 6 .
Figure 6.Load-displacement results of RCBs with different spacings of stirrups.

Figure 8 .
Figure 8. Load-displacement results of RCBs with different spacings of stirrups.

Figure 10 .
Figure 10.Load-displacement results of RCBs with different spacings of stirrups.

Figure 12 .
Figure 12.Load-displacement results of RCBs with different spacings of stirrups.

Figure 14 .
Figure 14.Load-displacement results of RCBs with stirrups spacing of 160 mm and altered quantity of CWP.

Figure 16 .
Figure 16.Load-displacement results of RCBs with stirrups spacing of 200 mm and altered quantity of CWP.

Figure 18 .
Figure 18.Load-displacement results of RCBs with stirrups spacing of 270 mm and altered quantity of CWP.

Figure 19 .
Figure 19.Assessment of energy dissipation for altered quantity of CWP.

Figure 20 .
Figure 20.Experimental and analytical results for shear capacity.

Table 1 .
Mixture design of RCBs.

Table 3 .
Experimental test results for stiffness and ductility values.

Table 4 .
Experimental test results for energy dissipation capacities.

Table 5 .
Comparison of experimental and analytical results for shear capacity.20%, and 30% improved the load-carrying capacity of RCBs, respectively, compared to the reference specimens.Consequently, adding CWP up to 10% to RCBs did not result in a significant reduction in the shear capacity.In other words, as CWP increased from 0% to 30%, the load-carrying capacity decreased between 30.3% and 59.4% compared to RCBs with stirrups spacing of 270 mm without CWP.However, reductions of 21.4%-54.3%and 18.6%-54.6%in the load-carrying capacity occurred, respectively, compared to RCBs with stirrups spacing of 200 mm and 160 mm without CWP.
Test samples Experimental result (ER) for shear capacity (kN) Analytical result for shear capacity (kN) ER/AR